Electrically heated oxidation catalyst particulate matter protection

ABSTRACT

A control method for a heating device of an oxidation catalyst is provided. The control method includes: estimating an accumulation of particulate matter on the heating device; and selectively controlling a switching device in electrical communication with the heating device based on the estimated accumulation.

FIELD OF THE INVENTION

The subject invention relates to methods, and systems for regenerating particulate matter in an electrically heated oxidation catalyst.

BACKGROUND

An oxidation catalyst device is provided in an exhaust system to treat unburned gaseous and non-volatile hydrocarbon (HC) and carbon monoxide (CO). The oxidation catalyst oxidizes the HC and CO under high temperatures conditions to form carbon dioxide (CO₂) and water (H₂O). A heating system is provided in the exhaust system to create the high temperature conditions for the oxidation process. Under various operating conditions, damage can occur to the heating system that prevents proper operation of the oxidation catalyst. Accordingly, it is desirable to provide methods and systems that prevent damage to the heating system and that ensure operation of the oxidation catalyst.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a control method for a heating device of an oxidation catalyst is provided. The control method includes: estimating an accumulation of particulate matter on the heating device; and selectively controlling a switching device in electrical communication with the heating device based on the estimated accumulation.

In another exemplary embodiment, an exhaust system of an engine is provided. The exhaust system includes: an oxidation catalyst; a heating device associated with the oxidation catalyst; and a control module that estimates an accumulation of particulate matter on the heating device, and that selectively controls a switching device in electrical communication with the heating device based on the estimated accumulation.

In yet another exemplary embodiment, a vehicle is provided. The vehicle includes: an engine; an electrically heated oxidation catalyst that receives exhaust gas from the engine; and a control module that controls current to the electrically heated oxidation catalyst based on an estimation of accumulated particulate matter in the electrically heated oxidation catalyst.

The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:

FIG. 1 is a functional block diagram of a vehicle including an engine and exhaust system in accordance with exemplary embodiments;

FIG. 2 is a dataflow diagram of an exhaust system control system in accordance with exemplary embodiments; and

FIG. 3 is a flowchart illustrating an exhaust system control method in accordance with exemplary embodiments.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

Referring now to FIG. 1, an exemplary embodiment of the invention is directed to a vehicle 9 that includes an exhaust gas treatment system 10, for the reduction of regulated exhaust gas constituents of an internal combustion engine 12. It is appreciated that the engine 12 is merely exemplary in nature and that the invention described herein can be implemented in various engine systems. Such engine systems may include, but are not limited to, diesel engine systems, gasoline direct injection systems, and homogeneous charge compression ignition engine systems.

The exhaust gas treatment system 10 generally includes one or more exhaust gas conduits 14, and one or more exhaust treatment devices. The exhaust treatment devices include, for example, an oxidation catalyst (OC) 18, a selective catalytic reduction device (SCR) 20, and a particulate filter device (PF) 22. As can be appreciated, the exhaust gas treatment system 10 of the present disclosure may include the OC 18 and various combinations of one or more of the exhaust treatment devices shown in FIG. 1 (SCR 20 and PF 22), and/or other exhaust treatment devices (not shown), and is not limited to the present example.

In FIG. 1, the exhaust gas conduit 14, which may comprise several segments, transports exhaust gas 13 from the engine 12 to the various exhaust treatment devices 18-22 of the exhaust gas treatment system 10. The OC 18 may include, for example, a flow-through metal or ceramic monolith substrate. The substrate may be packaged in a shell or canister having an inlet and an outlet in fluid communication with the exhaust gas conduit 14. The substrate may include an oxidation catalyst compound disposed thereon. The oxidation catalyst compound may be applied as a wash coat and may contain platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof. The OC 18 treats unburned gaseous and non-volatile HC and CO, which are oxidized to form CO and H₂O.

To aid in the oxidation process, an electrically heated device (EHD) 30 is disposed upstream of the OC 18. The EHD 30 provides the high temperature necessary to oxidize the HC and CO. Current is controlled to the EHD 30 periodically to initiate the oxidation process in the OC 18. In various embodiments, the EHD 30 may be constructed using a monolith filter that has an inlet and an outlet in fluid communication with the exhaust gas conduit 14. As can be appreciated, the monolith filter described herein is merely exemplary in nature and that the EHD 30 may include other filter devices known in the art.

As the exhaust gas 13 passes through the EHD 30, particulate matter of the exhaust gas may be deposited on the EHD 30. If too much particulate matter is accumulated on the EHD 30, the EHD 30 may short circuit when activated. Thus, the EHD 30 is selectively activated to regenerate the particulate matter that is deposited on or near the EHD 30. A control module 32 monitors the operating conditions of the engine 12 and/or the exhaust treatment system 10 and controls the current to the EHD 30 through a switching device 34. In general, the control module 32 controls the current by estimating the accumulation of particulate matter on or near the EHD 30 and selectively controls the switching device 34 based on the estimated accumulation.

Referring now to FIG. 2, and with continued reference to FIG. 1, a dataflow diagram illustrates various embodiments of an exhaust system control system that may be embedded within the control module 32. Various embodiments of exhaust system control systems according to the present disclosure may include any number of sub-modules embedded within the control module 32. As can be appreciated, the sub-modules shown in FIG. 2 may be combined and/or further partitioned to similarly control regeneration of the particulate matter on the EHD 30. Inputs to the system may be sensed from the engine 12, received from other control modules (not shown), and/or determined/modeled by other sub-modules (not shown) within the control module 32. In various embodiments, the control module 32 includes a particulate matter estimation module 40, and a heater activation module 42.

The particulate matter estimation module 40 receives as input engine parameters 44 (such as, but not limited to engine speed, fuel, barometric pressure, ambient air temperature, NO₂, Lambda, exhaust gas recirculation rate, exhaust flow, and exhaust temperature,), and exhaust parameters 46 (such as, but not limited to, exhaust flow, exhaust temperature, exhaust gas recirculation rate, Lambda, HC, NO₂, and cell density). Such parameters can be either sensed and/or modeled. The particulate matter estimation module 40 estimates the particulate matter generated by the engine 12, also referred to as the particulate matter rate based on the engine parameters. For example, the engine particulate matter can be estimated based on the engine parameters and estimation methods known in the art.

The particulate matter estimation module then estimates the particulate matter accumulated in or near the EHD 30 based on the engine particulate matter and the exhaust parameters 46. For example the particulate matter can be estimated based on exhaust parameters 46 and estimation methods known in the art.

The heater activation module 42 receives as input the estimated PM 48. The heater activation module 42 evaluates the estimated PM 48 to determine whether current should be controlled to the EHD 30. In various embodiments, if the estimated PM 48 is greater than a predetermined threshold, the heater activation module 42 activates the EHD 30 by controlling the switching device 34 to allow current to flow to the EHD 30 via control signal 50. The heater activation module 42 selectively controls the flow of current to the EHD 30 until the particulate matter has been regenerated successfully (e.g., by evaluating feedback parameters 49 that indicate, for example change in backpressure in the engine, or by evaluating exhaust temperature after the OC 18, etc.). At which point, the heater activation module 42 deactivates the EHD 30 by controlling the switching device 34 to prevent current to flow to the EHD 30 via control signal 50.

Referring now to FIG. 3, and with continued reference to FIGS. 1 and 2, a flowchart illustrates an exhaust system control method that can be performed by the control module 32 of FIG. 1 in accordance with the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated in FIG. 3, but may be performed in one or more varying orders as applicable and in accordance with the present disclosure.

In various embodiments, the method can be scheduled to run based on predetermined events, and/or run continually during operation of the engine 12.

In one example, the method may begin at 100. The engine particulate matter is predicted at 110; and the estimated PM 48 is estimated based thereon at 120. The estimated PM 48 is evaluated at 130. If the estimated PM 48 is greater than a predetermined threshold at 130, the EHD 30 is activated by generating the control signal 50 to the switching device 34 at 140. The EHD 30 remains active at until a threshold temperature is reached at 150 and the particulate matter has been regenerated at 160. Thereafter, the EHD 30 can be deactivated via the control signal 50 at 170 and the method may end at 180.

If, however, the estimated OC PM is less than the predetermined threshold at 130, there is not sufficient matter to create a thermal event within the oxidation catalyst and the method may end at 180.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application. 

What is claimed is:
 1. A control method for a heating device of an oxidation catalyst, comprising: estimating an accumulation of particulate matter on the heating device; and selectively controlling a switching device in electrical communication with the heating device based on the estimated accumulation.
 2. The method of claim 1, wherein the estimating the accumulation of particulate matter comprises: estimating particulate matter generated by an engine associated with the oxidation catalyst; and estimating the accumulation of particulate matter based on the estimated generated particulate matter.
 3. The method of claim 1, wherein the selectively controlling the switching device comprises: selectively controlling the switching device to a first position to permit current flow to the heating device when the estimated accumulation is above a threshold.
 4. The method of claim 3, wherein the selectively controlling the switching device comprises: selectively controlling the switching device to a second position to prevent current flow to the heating device when the estimated accumulation is below the threshold.
 5. The method of claim 3, wherein the selectively controlling the switching device comprises: selectively controlling the switching device to a second position to prevent current flow to the heating device when regeneration is complete.
 6. An exhaust system of an engine, comprising: an oxidation catalyst; a heating device associated with the oxidation catalyst; and a control module that estimates an accumulation of particulate matter on the heating device, and that selectively controls a switching device in electrical communication with the heating device based on the estimated accumulation.
 7. The exhaust system of claim 6, wherein the control module estimates the accumulation of particulate matter by estimating particulate matter generated by the engine; and estimating the accumulation of particulate matter based on the estimated generated particulate matter.
 8. The exhaust system of claim 6, wherein the control module selectively controls the switching device by selectively controlling the switching device to a first position to permit current flow to the heating device when the estimated accumulation is above a threshold.
 9. The exhaust system of claim 8, wherein the control module selectively controls the switching device by selectively controlling the switching device to a second position to prevent current flow to the heating device when the estimated accumulation is below the threshold.
 10. The exhaust system of claim 8, wherein the control module selectively controls the switching device comprises by electively controlling the switching device to a second position to prevent current flow to the heating device when regeneration is complete.
 11. A vehicle, comprising: an engine; an electrically heated oxidation catalyst that receives exhaust gas from the engine; and a control module that controls current to the electrically heated oxidation catalyst based on an estimation of accumulated particulate matter in the oxidation catalyst.
 12. The vehicle of claim 11, wherein the control module estimates the accumulation of particulate matter on the heating device, and selectively controls a switching device in electrical communication with the electrically heated oxidation catalyst based on the estimated accumulation.
 13. The vehicle of claim 12, wherein the control module estimates the accumulation of particulate matter by estimating particulate matter generated by the engine; and estimating the accumulation of particulate matter based on the estimated generated particulate matter.
 14. The vehicle of claim 12, wherein the control module selectively controls the switching device by selectively controlling the switching device to a first position to permit current flow to the heating device when the estimated accumulation is above a threshold.
 15. The vehicle of claim 14, wherein the control module selectively controls the switching device by selectively controlling the switching device to a second position to prevent current flow to the heating device when the estimated accumulation is below the threshold.
 16. The vehicle of claim 14, wherein the control module selectively controls the switching device comprises by electively controlling the switching device to a second position to prevent current flow to the heating device when regeneration is complete. 